This invention relates generally to fluid handling, and more particularly to a check valve for medical uses.
So-called needless injection ports, installed in infusion lines, provide sites where supplemental medication or other fluids may be introduced into the infusion line. Such ports actually contain quick-connect valves which close automatically when the medication syringe or line is withdrawn from the valve.
Representative prior U.S. Patents include U.S. Pat. Nos. 3,570,484, 3,831,629, 5,006,114, 5,049,128, 5,147,333, 5,201,725 and 5,242,432.
A needleless injection port must, of course, be and remain sanitary. It cannot admit air or other fluids accidentally, and must not drip or leak, either in use, or thereafter. It would be best to isolate moving parts of an injection port, as much as possible, from liquids flowing therethrough, and to provide a vent for gases in the valve, to prevent pressure differentials from occurring between the fluids (air and liquid) within the valve.
To prevent leakage, we surrounded all the moving parts of an injection port valve with an elastomeric sheath, constraining fluid to flow through the device only outside the sheath. This approach has the advantages of positively preventing liquid-air leaks, by eliminating sliding piston seals, but it creates a closed volume within the sheath which has to be vented, to prevent air pressure from being developed as the valve opens. The problem of venting is also addressed by this invention.